1. Field of the Invention
The present invention relates generally to a lens and more particularly to a zoom lens for use in a camera.
2 Description of the Background
Remarkable progress has been made in recent years for miniaturization of cameras. Major attempts heretofore made to miniaturize cameras have been to reduce the focal length of the lens used. However, if the focal length of a camera lens is reduced with respect to a fixed image plane or plate size, then the angle of view of the lens is increased, with the result that an image taken on the film is necessarily reduced in size. Therefore, when people are photographed at a substantial distance using a camera with such a lens, the faces of the people on the photoprint cannot easily be identified. In view of this problem, there has been a demand for a compact camera having a lens with a long focal length.
To meet such a demand, a camera with a bifocal lens and a camera with a zoom lens have been developed for accommodating a wider range of photographic conditions. The zoom-lens camera is advantageous over the bifocal-lens camera in that it can continuously vary the focal length, but is disadvantageous since it is more difficult to miniaturize than the bifocal-lens camera.
Various zoom lenses with a short back focus have been proposed to make rangefinder-equipped cameras with zoom lenses compact. Examples of such zoom lenses are disclosed in Japanese Laid-Open Patent Publications Nos. 56-128911, 58-184915, 58-184916, 58-224322, 58-137813, 58-184917, and 58-199312, for example.
However, cameras with such zoom lenses having short back focuses are larger in size when the zoom lens is stored or retracted than those cameras which have lenses storable into camera bodies, such as a camera with a collapsible lens barrel or mount or a self-erecting camera. The latter cameras are also large in size when in use because they employ lenses having long back focuses. Therefore, the use of a zoom lens in such cameras would inevitably result in a larger size.